Screening of PAHs and DDTs in sand and acrisols soil by a rapid solid-phase microalgal bioassay

Soil organic carbon stabilization in permafrost peatlands

In permafrost peatlands, the degradation of permafrost soil can raise soil temperature and alter moisture conditions, which increases the rate of loss of soil organic carbon (SOC). Here we selected three typical permafrost types that have very different active layer thicknesses but with soil originating from the same vegetation and which exist under comparable climatic conditions in the Da Xing'an mountain range: continuous permafrost, island permafrost, and island melting permafrost. To quantify the relative importance of control elements on SOC stabilization in these different permafrost types, we used correlation analysis to assess the relationship between organic carbon, physical and chemical properties and microorganisms, and explored the contribution of these factors to the accumulation of organic carbon. This study shows that the interaction between clay or silt, iron oxides and microorganisms have an important influence on the stability of organic carbon in permafrost peatlands.

Distribution and ecological risk assessment of organochlorine pesticides in sediments from four lakes of Heilongjiang Province, China

There is growing concern for the lake environment because polluted sediments may cause ecotoxicological effects. In the current study, persistent organochlorine compounds (OCPs), including hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs) and cyclodienes, were analyzed in core sediments taken from Huoshaohei Lake, Xihulu Lake, Wanghua Lake and Keqin Lake, Heilongjiang Province, China. The total OCPs concentrations ranged from 0.92 to 7.09, 0.15 to 9.95, 0.19 to 1.84 and 0.06 to 3.52 ng/g, respectively. The most dominant pollutants were the HCHs, high proportions of γ-HCH isomer indicating the recent input of lindane. The ratios of α-HCH/γ-HCH of four lakes are all lower than that in technical HCH mixtures indicating that there was input of lindane in the past several years, and the mean ratios of (DDE+DDD)/DDTs are all <0.5, suggesting recent release of DDT compounds. Compared with the corresponding ecological environmental quality guidelines from Ingersoll and base on the model of risk based corrective action environmental health risk assessment, the sediments from the four lakes poses a lower potential hazard to human health and the environment but still should be taken into account.

Ecotoxicological study on sediments of Mai Po marshes, Hong Kong using organisms and biomarkers

Sediments from Mai Po Ramsar site, Hong Kong were in general shown to be highly toxic based on the results of four toxicity tests (Microtox solid-phase test, Daphnia mortality test, algal [Microcystis aeruginosa] growth inhibition test and ryegrass [Lolium perenne] seed germination/root elongation test). Sediment of the mudflat (which is open to Deep Bay, i.e., the pollution source) was the most toxic while sediment of gei wai 24g (an enclosed freshwater pond) was the least toxic. Results of biomarker studies (tilapia hepatic metallothionein; glutathione (GSH) and EROD activity using H4IIE rat hepatoma cell) were also concordant with those in the toxicity tests. Significant liner relationships (p<0.01) were found between GSH contents in the rat hepatoma cells and PAHs, OCPs contents in the sediment extracts. It is recommended that the present suite of bioassays is useful and is biologically relevant for future ecotoxicological studies focusing on similar wetlands.